This week the TWiV team explains CRISPR/Cas, the immune system of bacteria and archaea, how novel viruses are discovered by deep sequencing of small RNAs, and the relationship between dry weather and outbreaks of West Nile virus infection.

Vincent, Dickson, Alan, and Rich answer listener questions about maternal infection and fetal injury, viral gene therapy, eyeglasses and influenza, filtering prions from blood, eradication of rinderpest, Tamiflu resistance of H1N1 influenza, bacteriophages and the human microbiome, H1N1 vaccine recalls, human tumor viruses, RNA interference, and junk DNA.

Vincent, Dickson, and Alan consider a broad spectrum antiviral against enveloped viruses, how a plant virus induces chemical signals in the host to maximize its spread, a new way to preserve viral vaccines at tropical temperatures, and the continuing story of XMRV and chronic fatigue syndrome.

Vincent, Alan, and Rich review recent outbreaks of mumps in the UK, US, and Israel, protection of mice against 2009 H1N1 influenza A virus by 1918-like and classical swine H1N1 vaccines, and a virus-like particle vaccine for chikungunya virus.

Vincent, Alan, and Rich are enthralled by movies of vaccinia virus plaque formation, then consider how repulsion of superinfection virions leads to rapid virus spread, and a therapeutic prostate cancer vaccine.

Vincent and Dickson continue virology 101 with a discussion of information flow from RNA to DNA, a process known as reverse transcription, which occurs in cells infected with retroviruses, hepatitis B virus, cauliflower mosaic virus, foamy viruses, and even in uninfected cells.

Vincent, Alan, and Matt discuss a project to study the RNA virome of Northeastern American bats, failure to detect XMRV in UK chronic fatigue syndrome patients, and DNA of bornavirus, an RNA virus, in mammalian genomes.

Vincent, Alan, and Rich talk about US government contract for freeze-dried smallpox vaccine, red squirrels in the UK threatened by poxvirus, and Marseillevirus, another DNA virus from amoebae built for comfort and speed.